Posted
by
Soulskill
on Sunday May 23, 2010 @08:06AM
from the eye-in-the-sky dept.

otter42 writes "It seems that X-37B couldn't stay hidden forever. Launched a few weeks ago, The Flying Twinkie disappeared shortly after separation. Now it has been found in an orbit that takes it as far north as 40 degrees latitude. No additional information has been found about the spacecraft's capabilities or purpose, except for a US Air Force statement that the satellite has no space-weapons purpose. The X-37B is intended to fly for 9 months at a time, opening the door to possible space longevity experiments in addition to its spying tasks."

I find it amazing they've created a spaceship that can stay up in the sky for up to 9 months at a time.

The article notes that "The X-37B can stay aloft for as long as nine months because it deploys solar panels for power, unlike the space shuttle."

I...doubt it's the solar panels alone which allow it to stay up there so long. Although, if it runs primarily on solar energy I'm frankly stunned at how powerful solar panels are. Arguably since they're getting pure sunlight rather than atmosphere diffused sunlight it's probably stronger, but still.

Also the reason I doubt the solar panels are the primary reason is due to the fact that the shuttles needed to add in a lot more weight for food/water which caused it to use more fuel plus be limited to how much food/water they could get up there. Even at best, I doubt the shuttle could've held enough food and water to last more than a month.

But yeah, the reduction in fuel weight is good to hear. If they're testing ion drives on it, this would be the most amazing real spaceship I've ever heard of.

But this thing is a very low earth orbit sattellite. It has a very fast shifting orbit, and it has much more athmospheric drag (though, granted, still not all that much). The orbit is "close" (certainly in space terms), low-latency, but a bit of a bitch to navigate in.

The International Space Station has a standard orbit of between 181 miles and 189 miles and only needs a boost a few times a year, while the X-37B was spotted at 255 miles up where the atmopshere is significantly thinner - 9 month longevity should not be hard to achieve, especially as the X-37B includes the ability to boost its orbit.

Dropping a rock from space isn't as straightforward of an idea as it sounds. Apologies to the Jerry Pournelle fans out there, but there are some problems that significantly reduce the cool factor.

First of all, drop the perception that each "rod" is a cheap, unpowered, purely-kinetic weapon, because the orbital physics don't allow it. De-orbiting an object (in a stable orbit, anyway) is not a free manuever, it costs thrust and therefore fuel burn to "slow" itself down so it drops out of orbit. Usually, the object is moving at a really high velocity--in LEO, it's at least 30,000 kph, maybe more. De-orbiting quickly (within minutes) means generating a large amount of force over a fairly short time interval. Given current technology, that means a rocket engine.

So each "rod" is basically just a missile launched from orbit. Instead of using thrust to against earth's gravity, the rocket thrusts against its own orbital inertia, which is *enormous* in LEO. Yes, after a certain point, the falling object becomes purely kinetic, but that doesn't change the fact that the weapon is basically an ICBM with a kinetic warhead instead of a nuclear warhead. The rocket engine could be somewhat smaller than an ICBM's, but still big enough to be a significant launch weight expense in the first place.

Second problem: The potential energy delta from LEO to the surface of the earth isn't big enough to accelerate the rod to hypersonic velocity, taking re-entry drag into consideration. You'd get a bigger explosion from dropping a MOAB, but at 1000x the delivery postage. You could raise the launcher's orbit, which increases the impact velocity, but which also enormously increases the delay between your lauch order and weapon impact. LEO is around 400 km from the surface, but geosync is somewhere above 30,000 km. De-orbiting could take hours, unless you hugely increase the power of the re-entry rocket, which means upscaling the size, weight, and expense per shot.

Finally, there's a non-phyics problem that wasn't even really an issue back when Pournelle came up with his original ideas: The politics of the "weapons of mass destruction" label. WMD is a sloppy-shit term that will get applied *instantly* by IR commentators and the press to any weapons system that has destructive power closer to a small nuclear bomb (~500+ t) than a MOAB (~10t). The fact that this isn't a nuclear weapon, or a chem/bio agent, will be totally irrelevant, because very few of the interested parties will know the difference. All that Joe Public (or Mohammed Al-Public, overseas) will understand is that the US has invented another unstoppable, super-technology killing machine.

So if your Rods from God are less powerful than a small tactical nuke, each shot would need to be cheaper than delivering an equivalent load of conventional ordnance--call if 10-50x MOABs. I seriously doubt that the economics would work in your favor, here, because boosting shit into orbit is insanely expensive, while big bombs are relatively cheap to make and drop.

On the other hand, if your Rods from God are as powerful or more powerful than a small tactical nuke, they become unusable on the battlefield because of the political costs. And it the Rods program is relegated to only being a strategic deterrent, it had better be cheaper than ICBMs/SLBMs. Again, I really doubt that the economics will work in your favor, for the same reasons.